(1) Field of the Invention
The present invention relates to a mobile station to which electric power is supplied by a battery and in which reduction in power consumption is required. The present invention particularly relates to a mobile station which reduces the power consumption of an operation of intermittent reception for intermittently receiving signals in a standby state.
(2) Description of the Related Art
In order to prolong a continuous calling time and a standby time, the low power consumption of a transmission/reception unit has been required from the past in a mobile station or the like of a mobile communication system. Therefore, there has been employed an intermittent reception system for intermittently receiving signals from a base station and the like in a standby state. The power consumption of the mobile station using the intermittent reception system can be reduced by halting the transmission/reception unit in a period other than a reception timing.
Japanese Patent Application Laid-Open No. 2002-368673 discloses that a high-resolution AD converter and a low-resolution AD converter are prepared as AD converters for converting a reception signal from an analog format to a digital format in a mobile terminal of a digital mobile communication system, and the power consumption is reduced by using the high-resolution AD converter and the low-resolution AD converter in a switchable manner on the basis of a current reception level and changes in reception level calculated by comparing the current reception level with a past reception level.
Further, Japanese Patent Application Laid-Open No. H11-317678 discloses that the state of radio waves in a mobile receiver is discriminated to set the mobile receiver at a continuous reception state in an intense electric field, to set the mobile receiver at an intermittent reception state in which a pause time and period is short in a weak electric field, and to set the mobile receiver at an intermittent reception state in which a pause time and period is long in no electric field in order to continuously receive signals, and power-saving effect can be obtained.
For example, when making a call to another mobile station, especially, when making a one-to-one call, there is a high possibility of receiving from the counterpart immediately after transmission. As the time passes after transmission, the possibility of receiving from the counterpart becomes low in many cases. This is because response information for transmission information is returned from the counterpart in many cases.
Further, immediately after receiving from another mobile station, there is a high possibility of receiving from the another mobile station or other mobile stations. As the time passes after reception, the possibility of receiving from the another mobile station becomes low in many cases. This is because additional information for transmission information from the another mobile station is transmitted from the another mobile station, or response information is returned from the other mobile stations in many cases.
In the past, the interval of intermittent reception was not changed in accordance with an elapsed time after completion of transmission or completion of reception. Even if an elapsed time after completion of transmission or completion of reception became considerably long, the efficiency of power consumption was poor due to a short interval of intermittent reception.
There is no description on intermittent reception of a mobile receiver in Japanese Patent Application Laid-Open No. 2002-368673. Further, Japanese Patent Application Laid-Open No. H11-317678 discloses intermittent reception of a mobile receiver in accordance with the state of radio waves, but does not disclose to perform intermittent reception in accordance with an elapsed time after transmission or reception by a mobile station.
An object of the present invention is to provide a mobile station which reduces the power consumption of an operation of intermittent reception in accordance with an elapsed time after transmission or reception.